This invention relates to roller transducers and in particular to an ultrasonic roller transducer assembly which, when used in pairs, generate signals to form an ultrasonic image of an article passing between the pair of ultrasonic roller transducer assemblies.
Wood imaging apparatus of the prior art included an air gap between the imaging apparatus and the wood, but air is a poor transmission medium for coupling acoustic energy into the wood. Because of an acoustic impedance mismatch, air is not an efficient energy transfer medium. Visual scanning with cameras had been tried to observe surface characteristics and predict the location of internal defects within the wood, but this technique was not reliable.
Prior art patents include U.S. Pat. No. 3,384,767 issued May 21, 1968 to James S. Arnold et al. and assigned to Stanford Research Institute, disclosing an ultrasonic transducer employed for evaluating a bond between materials which are fastened together and a method and means for exciting such a transducer. The transducer pairs are made of a cylinder of barium titanate having rubber around the periphery for the purpose of transmitting or receiving mechanical vibrations. The transducers are mounted to be rotatable so they can roll over a structural material such as plywood having bonds. However, it does not disclose the use of a 1-3 piezocomposite transducer disposed in interlocking core sections around which an outer tire portion rotates.
In U.S. Pat. No. 3,780,570, issued Dec. 25, 1973 to Jack T. Collins and assigned to Automation Industries, Inc., an ultrasonic inspection device is described for testing flat bonded panels such as plywood. A plurality of transmitting search units are provided on one side of the panel and a plurality of receiving search units are mounted on the opposite side of the panel. Each search unit includes a roller which is adapted to roll across the surface of the panel. An ultrasonic transducer is mounted on the drum. In order to acoustically couple the transducers to the surface of the panel, a wear receiving member such as a tire may be provided around the outer or active face of the transducer. This tire may be permanently mounted on the outside of the transducer, such as by bonding it directly thereto. The tire is preferably made from a resilient material transparent to ultrasonic energy. Also, the acoustical impedance of the tire should closely match that of the transducer. The transducer is intimately acoustically coupled to the panel. However, it does not describe a pair of ultrasonic rollers, one on each side of a panel for generating an image of the panel wherein only the outer portion of the roller rotates about a plurality of core sections each having a 1-3 piezocomposite element.
In U.S. Pat. No. 4,750,368, issued Jun. 14, 1988 to Dwayne M. Shearer et al., and assigned to Weyerhaeuser Company, a method is described for on-line nondestructive determination of the internal bond strength of composite panel products by impinging an ultrasound pulse against the panel by an upper transducer assembly and receiving a transmitted pulse at second transducer assembly. The received signal strength, temperature, and panel thickness are entered into an algorithm from which the internal bond may be calculated. Each transducer assembly comprises a piezoelectric transducer. However, it does not disclose a roller transducer comprising a plurality of adjacent interlocking core sections, each of the core sections having a 1-3 piezoelectric transducer and an outer tire portion rotating about the core section, for testing a wide surface area of a board.
In U.S. Pat. No. 5,760,308 issued Jun. 2, 1998, and U.S. Pat. No. 5,804,728 issued Sep. 8, 1998 to Frank Carroll Beall et al. and both assigned to The Regents of the University of California, an apparatus is described for detecting internal bio-deterioration in round wood materials used in various applications. The method includes the steps of securing a pulsing transducer adjacent one point on the surface of the round wood and securing a receiving transducer substantially diametrically opposite to the pulsing transducer. The ultrasonic transducer transmits ultrasonic signals through the round wood which propagate through possibly deteriorated areas throughout the wood. The receiving transducer receives the propagating ultrasonic signals, and a plurality of acousto-ultrasonic parameters contained in the received ultrasonic signals are processed and analyzed. However, they do not disclose the application of 1-3 piezocomposite transducers in a plurality of core sections with interlocking structures and having an outer portion which rotates around the core sections.
In U.S. Pat. No. 6,092,418, issued Jul. 25, 2000 to Mark E. Schafer et al. and assigned to Perceptron, Inc., a method and apparatus is described for detecting and characterizing splits in logs. A wooden log is moved in a translation direction with respect to a measurement assembly by one or more driven rollers that support the wooden members from underneath. The measurement assembly comprises a transmitting and a receiving ultrasonic transducer encased in rollers such as may roll against the surface of the wooden members. As shown in FIG. 15, the ultrasonic transducers include a transducer element held in a coupling fluid such as oil as contained by the inner surface of a rotating wheel. The outer surface of the wheel provides a series of radially extending spikes 84 to penetrate bark of the log which generally inhibits the transmission of ultrasonic energy. However, it does not describe a roller transducer having a plurality of interlocking core sections, each having a transducer and an outer tire portion which rotates about the core sections for testing a wide surface area of an object such as a board or a log.
It is therefore an object of this invention to provide an ultrasonic roller transducer assembly having an outer portion comprising a nylon roller tube surrounded by a urethane tire that rotates about an inner portion comprising a plurality of core sections having transducers.
It is another object of this invention to provide a 1-3 piezocomposite element in the transducer of each core section of the roller transducer assembly.
It is a further object of this invention to provide a fluid within the ultrasonic roller transducer assembly for providing a continuous path for the ultrasonic energy to be transmitted out of the assembly and into a scanned article.
It is still another object of this invention to provide a pair of spaced apart ultrasonic roller transducer assemblies parallel to each other for generating an ultrasonic image of an article passing between the pair of transducer assemblies.
It is an object of this invention to provide a first transducer and a second transducer adjacent to the first transducer for generating signals for transmission to a moving object such as a log and detecting reflected signals from the moving object in order to calculate the velocity of the moving object.
It is another object of this invention to provide a roller transducer having a roller tube spaced apart from a combined core/hub assembly to minimize laminar flow of the fluid in the space between the roller tube and the combined core/hub assembly thereby minimizing related electrical noise.
These and other objects are accomplished by a roller transducer assembly comprising at least one core section having at least one transducer positioned in the core section to transmit or receive signals, means for stiffening the core section and securing the core section to a hub of the assembly, a roller tube surrounding and spaced apart from the core section, the roller tube being secured to each end of the assembly, means, sealed between the roller tube and an outer portion of each core section, for providing a continuous path for energy transfer to and from the transducer, and means for constraining radial and axial movement of the roller tube at least at one end while permittingrotation of the roller tube about the hub. The core section comprises means for constraining radial movement between the core section and the hub. The roller tube comprises a material for enhancing energy transfer. The roller tube comprises an outer portion of a soft material for enhancing the continuous path for energy transfer to and from the roller transducer assembly. The energy transfer means comprises a medium for efficient signal transmission. The energy transfer means comprises a fluid. Each core section comprises a cavity for receiving the transducer or the transducer and associated electronics. Each core section comprises a hollow center portion for channeling electrical leads to a connector at an end of the assembly. Each core section comprises means for transferring impact loads from the roller tube to the stiffening and the securing means. The core section, the roller tube, and the energy transfer means comprise materials to minimize energy reflections at each interface of the materials. The assembly comprises a noncontinuous contact surface above the transducer to improve inter-element separation. The roller transducer assembly further comprises means for generating and processing signals to and from the transducer. The roller transducer assembly further comprises a second transducer positioned adjacent to the first transducer in each core section, means for generating a first signal coupled to the first transducer for transmission to the object moving in a predetermined direction adjacent to the transducer assembly, means for detecting the first signal reflected from the moving object, means for generating a second signal coupled to the second transducer for transmission to the object, means for detecting the second signal reflected from the moving object, and means for calculating the velocity of the moving object from the propagation time of the detected first signal and the detected second signal sent to and reflected from the moving object.
The objects are further accomplished by an apparatus for producing an image of an object comprising a first roller transducer assembly having at least one core section, each core section comprises a transducer for transmitting signals toward the object, a second roller transducer assembly, positioned a predetermined distance from the first roller transducer assembly, comprises at least one core section and each core section comprises a transducer for receiving signals transmitted by the first roller transducer through the object moving between the first roller transducer assembly and the second roller assembly, means for processing the signals received by the second roller assembly, and means connected to the processing means for displaying an image of the object.
The objects are further accomplished by an ultrasonic roller transducer assembly comprising a plurality of core sections, each of the core sections comprises a transducer positioned in each of the core sections to transmit or receive signals, a plurality of rods, each of the rods passes through one of a plurality of rod holes on the core sections, each of the plurality of rods being secured to the assembly at each end of the rods, a roller tube surrounding and spaced apart from the plurality of core sections, the roller tube being secured to an end cap of the assembly, a tire encircling the roller tube for contacting an object, a fluid, sealed between the roller tube and the outer portions of the plurality of core sections, for providing a continuous path for energy transfer to and from the transducer of the core sections, and a bearing positioned around a neck of a hub attached to each end of the assembly enabling the tire and the roller tube to rotate about the plurality of core sections. The core sections comprise a stiff, engineering polymer, such as Delrin (Registered Trademark of E. I. DuPont de Nemours and Company of Wilmington, Delaware). Each of the plurality of core sections comprises means for interlocking adjacent core sections. The transducer comprises an acoustic transducer made from piezoelectric material or electrostrictive material. The roller tube comprises a stiff, acoustically-transmitting polymer material, such as nylon. The tire comprises a compliant acoustically-transmitting polymer, such as soft polyurethane. The fluid comprises an inert, insulating liquid, such as silicone oil. Each of the plurality of core sections comprises a cavity for receiving the transducer and a foam section disposed adjacent to the transducer for providing a low impedance backing to reflect energy out of the core sections. Each of the plurality of core sections comprises a hollow center portion for channeling electrical leads to a connector at an end of the assembly. Each of the plurality of core sections comprises a roller bearing positioned around each of the rods passing through the core sections for absorbing impact loads from the object. The plurality of core sections, the roller tube, the tire, and the fluid comprises approximately the same acoustic impedance for minimal reflections at each material interface. The tire comprises a plurality of notches above the transducers to improve inter-element separation. The ultrasonic roller transducer assembly further comprises means for generating and processing signals to and from the transducer.
A roller transducer comprising a combined core/hub assembly having a flat surface on a portion of the circumference of the roller transducer, a hollow cylindrical center portion, and an insert secured to the flat surface, a cavity disposed in the roller transducer under the inset, a transducer assembly positioned in the cavity under the insert having electrical leads which are fed to the hollow cylindrical center portion of the roller, a roller tube surrounding and spaced apart from the combined core/hub assembly, the roller tube being secured at each end of the roller transducer, and a fluid, sealed between such combined core/hub assembly and the roller tube, for providing a continuous path for energy transfer to and from the transducer assembly. The insert comprises a flat inner surface and a flat outer surface. Also, the insert comprises an outer spherical surface and an inner flat surface or an outer trapezoidal surface and an inner surface having a cavity for receiving a portion of the transducer assembly. The transducer assembly comprises a piezoelectric or an electrostrictive transducer, preferably a 1-3 piezocomposite transducer.
The objects are further accomplished by an acoustic velocity sensor positioned in a cavity of an ultrasonic roller transducer assembly comprising a first transducer, a second transducer positioned adjacent to the first transducer, means for generating a first signal coupled to the transducer for transmission to an object moving in a predetermined direction adjacent to the ultrasonic roller transducer, means for detecting the first signal reflected from the moving object, means for generating a second signal coupled to the second transducer for transmission to the moving object, means for detecting the second signal reflected from the moving object, and means for calculating the velocity of the moving object from the propagation time of the detected first signal and the propagation time of the detected second signal sent to and from the moving object.
The objects are further accomplished by the method of providing a roller transducer assembly comprising the steps of providing at least one core section having at least one transducer positioned in each core section to transmit and to receive signals, stiffening the core section with means extending through each core section and securing the extending means and the core section to a hub of the assembly, positioning a roller tube around and spaced apart from each core section, the roller tube being secured to each end of the assembly, providing a fluid between the roller tube and an outer portion of each core section to have a continuous path for energy transfer to and from the transducer, and constraining radial and axial movement of the roller tube at least at one end which permits rotation of the roller tube about the hub.